<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta http-equiv="X-UA-Compatible" content="IE=edge" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Document</title>
  </head>
  <body>
    <script>
      /* 
        GO {
          a:undefined
          demo:fn
        }

      */
      a = 100
      function demo(e) {
        /* 
          AO {
            e:undefined 1
            a:fn
            b:undefined
            c:undefined
          }
        */
        function a() {}
        arguments[0] = 2
        console.log(e) //2
        if (a) {
          var b = 123
          // 只会提升var c 函数表达式不执行预编译
          var c = function () {}
        }
        var c
        a = 10
        var a
        co
        nsole.log(b) //123
        f = 123
        console.log(c) //function() {}
        console.log(a) //10
      }
      var a
      demo(1)
      console.log(a) //100
      console.log(f) //123
    </script>
  </body>
</html>
